One of the Navy’s strangest craft, unromantically titled YD 171, might be called by the more meaningful and appealing name of “Seagoing Samson,” for it can toss freight-train weights about like a skilled juggler. The YD 171, reassembled at Long Beach Naval Shipyard, is one of the largest floating cranes in the world. Twice as tall as the Leaning Tower of Pisa, the crane stands 374 feet high with its boom raised.
The crane, one of four built in Germany during the war, was awarded to the United States under the authority of the Tripartite Naval Commission. One of the original four was sunk. Another, scheduled for award to Russia, was not complete when the war ended. The remaining two, used at Kiel by the Germans for submarine construction and repair, were taken over by the British. It is one of these bulging biceps of the briny deep that was assigned to the Navy.
By flexing its muscles recently in a 10 per cent overload test, Samson reached 59 feet over its side and heaved nearly 425 net tons (2000 pounds each) into the air to prove its strength. That 848,900 pound test, equivalent to lifting 283 automobiles in the air at one time, was as large as any ever accomplished by a water-borne crane.
Self propelled, the crane can slither through the water forward, backward, or sideways. It has no rudder, yet can turn in its own 205-foot length. It can make a complete circle in 54 seconds. As handy as if it were hinged in the middle of its 109 foot beam, the YD is maneuverable by virtue of its three Voith-Schneider propellers—two at its stern and one at its bow. The propellers, unlike conventional screws, rotate on a wheel whose axis is perpendicular to the keel. Six tapered bronze blades that look like six-foot Irish shillelaghs are attached to the rotating wheel to flail the water for propulsion. The blades thrust in the direction desired and feather until in position once more. By variable pitch of the blades, controlled from a pilothouse in the derrick structure, the diesel-electric craft can maneuver itself into narrow berths without the assistance of a tug.
Resting on a mammoth compartmented pontoon, the weight lifter is of the type known in marine engineering as a double-jib derricking crane. It consists essentially of two parts. The fixed part, shaped like a pyramid, transfers all operational forces from the derrick to the pontoon. The rotary part, shaped like a bell, fits over the pyramidal support structure. The hoisting system is connected to the upper part of the bell and the device is balanced by counterweights. Four hundred tons of stationary weight is built-in; another 200 ton weight operates on a pendulum to accomplish level luffing—maintaining the block of the boom in a horizontal path as it moves radially.
For heaviest loads, two 175 metric ton (2,204 pounds each) capacity hooks may be linked together to lift 350 ton loads from 26 feet below the waterline to 170 feet in the air. For relatively light loads like a carload of armor plate, two 30-ton hooks and one 10-ton hook serve as auxiliaries. The auxiliary hooks move in and out on the boom by trolleys.
Up to a height of 102 feet above water, no portion of the crane extends beyond the pontoon fender so that collisions with other vessels moored alongside cannot occur.
The crane operator works in a “clear vision” booth high in the rotating structure. Transparent dials on his switchboard light up like a pinball machine to indicate the condition of hoists in operation, leaving the operator freedom to concentrate on crane operations without having to rely upon memorized data. “When we made the overload test, I could feel the crane heel over like a pole vaulter clearing his mark,” the operator says. “The operator’s cabin jutted out over the side of the pontoon and I could see waves lapping up at me 90 feet below. It was all right, though,” he concludes, “we still had two and a half feet of freeboard left on the pontoon. Less freeboard would have been too little, the design people tell me.” The supporting pontoon has a depth of seventeen feet; it has no trimming tanks; and maximum safe inclinations have been set up for various weights at different positions on the boom. The equipment has safety features built in, but none takes the place of alert operating personnel.
Hoists can be slowed to speeds not perceptible to the human eye for working in narrow spaces. On the other hand, the crane can operate with the speed of a bounding gazelle to toss, say, a thirty-ton turret into the air and lower it away at 56 feet per minute, or to kick a mere five-ton anchor about at 168 feet per minute.
Hoisting gear is operated by a 440-volt DC motor whose power is supplied by converters connected to the main AC generators. The main cable, one and seven- eighths inch galvanized cast steel 8X36 wire with a hemp core, is ten times reeved on two blocks at hoists. Inside the derrick structure, the cable drums, ten feet in diameter and thirteen feet long, receive the wire in grooves in one layer. Cable drums may be synchronized with a coupling device when both of the largest hooks are to be used together for extremely heavy lifts.
Though the crane, valued at three million dollars, is worth more than thirteen times as much as the Navy spent to put it into shape, the giant gave the Navy plenty of headaches before it was ready for operation.
It was towed by Navy tugs from Bremerhaven to the Pacific Coast. All of the superstructure above the butt boom—the lower part of the derrick—had to be removed to keep the boom from collapsing in passage. Even stripped of its upper works, the crane was over 130 feet high. Built-in fenders of the pontoon had to be removed to allow it to pass through the Panama Canal.
When the stripped-down crane arrived in Long Beach, workmen set about repairing minor bomb damage to the hull and upper works. Public Works engineers turned to checking the design, converting metric measurements, and translating foreign terms. Much engineering data considered vital by the Navy was omitted from captured German prints. American engineers, calculating stresses and strains, made new plans and operating instructions, and figured new safety factors.
The superstructure arrived separately and had to be assembled on the butt boom. The Navy’s then largest crane ship, AB 1, was assigned the job of lifting the heavy, high tensile steel parts into place. With a 250- ton capacity boom, the crane ship was powerful enough to lift the parts; but with the German crane in the water alongside her, AB 1 could not lift high enough to reach the tree-top tall boom of YD 171. Neither sky hooks nor a cloud hoist were available. The Navy was up in the air; the crane’s jib-booms and telescope coupling, unfortunately, were not.
Finally one of the engineers on the project had a bright idea: if AB 1 could not be made higher, then make the German crane lower. The Moreell drydock, he said, is like an enormous bathtub. Place the German crane in the tub, pump it dry, and the crane would drop almost fifty feet below sea level to the drydock floor. The crane ship, he pointed out, remaining at sea level outside the caisson of the graving dock would then reach high enough for the job.
Swell idea, everyone agreed. The German plan for docking, however, was not complete. Positions of various underwater openings of the 5000-ton displacement pontoon were not accurately located. A new docking plan had to be devised by Public Works. Plans for ballasting the forward part of the pontoon had to be made to insure even docking, then for removing the ballast to prevent hogging as it settled to rest on keel blocks. To complicate matters, nature added to the Yard’s difficulties by providing a high wind. Only alter the ballast was removed, the dock pumped dry, and the hull inspected did official anxiety subside. The giant had drydocked perfectly. Rear Admiral Thomas Wynkoop, Shipyard Commander, and Captain H. W. Baumer, Public Works Officer, looked at the mammoth crane as if to say, “Thank you, Samson, for behaving this once.”
AB 1, the crane ship which was once the U.S.S. Kearsarge, pride of the battle fleet around the turn of the century, moored alongside the dock. Its boom was then high enough for the operation.
The naturalized crane was stationary on keel blocks in the graving dock. The floating crane, however, was water borne, subject to roll and pitch with the waves. Travelling cranes, operating along the edge of the dock to assist in the reconstruction, were stable.
The AB 1 heeled over slightly and surged with the waves as it lifted the first 350,000-pound piece of the German boom into place. The section had to be attached to the derrick with two heavy pins. The steel pins, eighteen inches in diameter, each weighed more than ten heavy men, and fit with twenty-one thousands of an inch clearance. Furthermore, both pins had to be set at the same instant to prevent twisting the boom. Water traffic was stopped.
“It was something like a nervous giant’s having one foot on land and the other in a canoe as he placed a new 175-ton balance staff in his watch,” O. A. Faircloth, Master Rigger supervising the job, says. “The watch was steady, but the giant and balance staff moved with every surge.”.
Riggers judged a three-inch surge of the crane ship, timed their action carefully, and hammered the pins home with hydraulic jacks. The first operation required fifty-two minutes after the member was lifted into the air. “It was a matter of outguessing the surge,” Faircloth says. “We expected to take hours for that part of the job alone.”
As the job progressed, erecting structural members became more difficult. To place the jib-booms, auxiliary hooks of the crane ship had to be overloaded by eight tons. Riggers, perched 200 feet in the air with their hands and heads hanging down, had no place to go as the jib-booms swung into position to be pinned with eight-inch pins. An afternoon Long Beach wind sprang up, not so violent, perhaps, as the one which interfered with drydocking, but nonetheless nerve wracking. The crane ship danced a hornpipe, surged back and forth, and riggers fought the wind, tide, and surge. “Riggers clung to the booms by their imaginations for three and a half hours before we succeeded in pinning the jib-booms,” Faircloth says.
As the hoisting structure of the YD went into the air, the rig had to be shortened by removing temporary erection links. All this was headache enough, but when the boom was raised to 14°, the crane’s counterbalance mechanism had to be attached as the second lift. The counterbalance mechanism weighed 47 tons, and an error at this point could have meant curtains for Samson; also, 200 tons of concrete weights were added progressively in units of 10 and 15 tons. The crew of an LSM drydocked with the crane was ordered ashore for safety. Riggers felt their way along with feeler gauges, once more outguessed nature, and jacked the pins into place. They then removed the remaining erection links, brought the boom under its own power and hooked the levelling link into place.
The remaining work, straight rigging of cables to blocks, hooks, and drums, was no simple matter, but not so difficult as that summarized above. “Never did a job I was more proud of than this one. And to do it I had some of the best riggers in the world, all trained in the fact that safety comes first and showmanship plays no part in the rigging game,” Faircloth says. “When it was over I took a deep breath and went fishing.” Not a man was hurt on the job.
The crane is now being tested with different weights and varying conditions under the supervision of F. A. Williams, formerly of Bremerton, Washington. An electrical engineer connected with the Long Beach Yard, Williams jots figures in his notebook with every lift and swing to plot charts on the crane’s operational characteristics.
Before long, Williams says, its tests completed, the floating crane will be heaving away on construction and repair jobs on the Navy’s largest ships.